Important New Findings on Genetic Modifiers of Progressive Retinal Atrophy in Dachshunds
Dachshund breeders should take note of an important new study on the genetics behind progressive retinal atrophy (PRA) in dogs. PRA is an inherited eye disease that causes degeneration of the retina's photoreceptor cells, eventually leading to blindness.
The study, published in the journal Animal Genetics, examined the frequencies of two genetic variants - RPGRIP1ins44 and MAP9del - across 132 dog breeds. These variants act as genetic modifiers that influence the development and progression of a form of PRA caused by the RPGRIP1 gene, called RPGRIP1-cone-rod dystrophy (RPGRIP1-CRD).
Here are the key findings relevant to Dachshund breeders:
1. Both the RPGRIP1ins44 and MAP9del variants were found to be relatively common in the Miniature Longhaired Dachshund breed. This breed had the highest probability (around 1 in 1,100 dogs) of having dogs homozygous for both variants.
2. Dogs homozygous for just the RPGRIP1ins44 variant tend to have a relatively mild form of retinal degeneration that may not cause noticeable vision impairment. The real vision problems occur when a dog is homozygous for both RPGRIP1ins44 and MAP9del.
3. There appears to be selective breeding pressure against dogs being homozygous for both variants, likely because breeders have avoided breeding affected dogs with vision issues over time.
4. The findings suggest both variants arose long before modern dog breeds were created and established as distinct populations.
Avoiding breeding dogs homozygous for both variants will be important to reduce the incidence of the more severe, early-onset form of RPGRIP1-CRD. Unfortunately, there is still no commercially available DNA test for the MAP9del mutation. Dachshund breeders can still make more informed decisions to progressively reduce the burden of inherited retinal disease in their breed over time. Use of the KC/BVA clinical eye-screening test conducted by veterinary ophthalmologists is strongly recommended as PRA is not the only eye disease affecting the breed. Dachshund Health UK has been subsidising these tests for several years.
Although the study indicates that dogs homozygous for just RPGRIP1ins44 may have minimal vision issues, breeders should keep in mind that routine, commercial testing for the MAP9del variant is not yet available, and therefore the only current means of minimising the risk of breeding dogs that could be homozygous for both variants is to continue to reduce the frequency of RPGRIP1ins44 within the breed.
The paper was written by Cathryn Mellersh and Jonas Donner and is available here:
We are grateful to Cathryn for reviewing this blog post prior to publication.
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